I too started seeing rendering
artifacts in my area as soon as I upgraded to this Beta. Many of them take the form of grey lines, the same width as regular roads, but they appear to run between geometry nodes on the same road or between two different roads.
Also, several of the roads in my area (including minor & major highways) have places where they double back over themselves repeatedly--and when navigating, if those segments are part of the route the entire "scribble" is highlighted. The car continues to move along the actual road as usual, but it's as though the road segments have a bunch of spurious geometry nodes, or they were read out of order when the tile was generated.
The livemap and editor map do not show any of these errors, and since they seem to come and go as the map moves, my conclusion is that it's a bug in the client's drawing code, rather than in the tile-rendering process. I don't know the full extent of the problem because I have only driven in
this area since upgrading to this Beta, but it's a good place to start looking. Navigating from Main St in Rockport to Eastern Ave/Route 128 in Gloucester shows a couple really messed up places, plus both rotaries (roundabouts) in the area are being drawn on the client with Major Highway segments running right through the middles of the circles in a crosshatch pattern.
On a more positive note, the display does seem to have sped up enough to (mostly) eliminate the display lag and server timeout issues that I have
reported in previous versions, starting with the first 3.x beta that I tried.